Photograph by NASA
The Boomerang Nebula, also called the Bow Tie Nebula, about 5,000 lights away in the constellation Centaurus.

Space is a dusty place

August 31, 2009 at 09:38 AM

BY PETER BECKER

Just look at that dust!

The bane of (most) homemakers, dust seems ever present. People living by a busy highway get lots of it. We constantly try and move it around, vacuum it up, brush it off.

One might not expect dust when looking at the stars. Of course we have dust in our own atmosphere, which is part of the reason we have red sunsets and sunrises. As much as hope for a clear sky, however, the stars themselves share space with enormous amounts of dust. In fact, the Milky Way Galaxy is full of dust.

Astronomers use another term for the dust clouds: nebulae (plural for nebula). These cosmic clouds might consist of gas or dust. Vast dusty areas permeate the star-packed arms of the grand spiral shape of our galaxy.

If you are away from city lights and look up on a moonless summer night, you will see the hazy, billowing Milky Way Band stretching across the heavens. Late August is an excellent time to see it, during the evening, as it stretches from the northeast, overhead and down to the southwest. You are witnessing not only distinct masses of stars populating nearby arms of this grand spiral shape, you are also seeing nebulosity.

Notice along this diffuse, dimly lit band, which resembles somewhat a pillar of white smoke, that the band seems to be split into two. This is most noticeable from the constellation Cygnus the Swan, overhead, down through the constellation Aquilia the Eagle, in the south. This dark split is not an actual tear in the Milky Way. It is dark nebulae; a vast stretch of dust is blocking your view of the stars behind it.

Near the horizon (this assumes you live in mid-northern latitudes, by the way), the Milky Way covers the constellation Sagittarius the Archer. This area is much better seen in the far south where Sagittarius is high in the sky. Away from the murky dust of our own atmosphere when viewed low to the horizon, the Milky Way is revealed as a bright, wide area. This is actually the central hub of the Milky Way, where the spiral arms emanate. Huge amounts of nebulae in this region prevented astronomers from peering deep into the center of the galaxy, until infrared photography was employed. Infrared light is of longer wavelength and gets around the tiny dust particles; the result is images of stars not otherwise seen.

Study of the stars close to the center of the galaxy revealed the suspected presence of what must be a super-massive “black hole” where matter and energy cannot escape. Stars near it revolve around this point at incredible speeds.

The main stars of Sagittarius are easily pictured as a teapot. The Milky Way Band seems to be pouring from the teapot spot like steam. You need to be away from the city and there must not be any moon to be able to see this.

Many patches of nebulae are visible in backyard telescopes. Most of them shine by reflected starlight. Most nebulae, however, are seen only by long-exposure photography.

While astronomers have them catalogued by reference numbers, such as NGC 7000, many of those that are favorites of amateur astronomers are nicknamed, usually describing what they look like. It’s similar to gazing at fair-weather clouds and finding a duck or bunny or bust of Beethoven. NGC 7000 is also called the North American Nebula for its uncanny resemblance to the continent. We also have the California Nebula, Swan Nebula, Horsehead Nebula, Trifid Nebula, Ring Nebula and Great Nebula of Orion, to name just a few.

As much as we can enjoy finding dusty nebulae with our backyard telescope and a good star map, Earth dust must be kept off your telescope lenses and mirrors. Keep your telescope or binoculars covered when not in use. When your lens or mirror requires cleaning, treat them with great care as you would your eyeglasses. Distilled water should be used, as well as a lint-free cloth. Dab very gently. Be careful not to touch the optics with your fingers.

Full moon is on Sept. 4.

The writer may be contacted at .(JavaScript must be enabled to view this email address).

Keep looking up!

Comments :: Terms :: .(JavaScript must be enabled to view this email address)